I would like to offer two suggestions:

[Bye_Kitty]

1. Team play. I have always wanted to play this with, not against, a friend.
How it works:
A friend is invited then the group leader starts the match, clicking the Dual Play button.
In Dual Play screen, the group leader can choose whether to play in casual (against ai or players) or ranked.
When the match begins, all features retain the same value with a few minor changes:
1. Names of both sides of opponents are displayed in their respective locations.
2. After the coin is flipped and cards drawn, each side can play up to 2 cards before the turn ends.
3. No major changes to the UI. Player 1 does not see the cards of ally and when the ally plays a card, it appears from offscreen, and vice versa.
4. The graveyard on both sides of the field are shared with their respective ally.

2. Nationalistic approach to decks. While this is achievable with certain factions at present, it is considered difficult or not possible with Northern Realms.
How this feature works:
1. The faction display (represented by the icon and banner) shown in the top-left section of cards is made more faction specific. The banner is changed to
represent the actual faction (i.e red for Redania) while the icon has no change and represents the Northern Realms.
2. More cards are added and with similar or same stats but different artworks and banners. For example, there are multiple Standard Bearers card in the
Northern Realms deck and one can see that they are only different in artwork and banner colour.

 

[FDC-Crumble]

Nice set up.. I would like to change one thing.

You state in point 3 the following: "Player 1 does not see the cards of ally and when the ally plays a card, it appears from offscreen, and vice versa. "

I believe that the whole ting of coöp playing with a friend is to complement each other en use each others deck to gain an advantage. Besides... If you play together you can always talk to each other about what to play, how and why.